For me the speech was great, but even better was all the non verbal acting he (and jamie) did throughout the episode. You could see all the emotions going through his character through the whole process without him saying a word.
I have to agree with everything said here. You can see him slowly getting more and more worked up about all the BS that's happening, full well knowing Cersei's just playing her shit cards.
So after watching the most recent episode with that amazing speech. My buddies and I were talking about the possibilities of who each party would call down as their champion. Keep in mind with zero knowledge of the books I think Tyrion is going to call Oberyn, and I think Tywin(daddy) is going to call the mountain to fight for his side.
Possibly a form of punishment? Previous episodes Oberyn believed that his sister etc was killed because Tywin ordered the kill, but if he gives Oberyn the mountain in combat for the trial...so many things get accomplished probably.